Graph: How Coffee Drank Soda's Milkshake

Ten years ago, Americans drank enough soda every year to fill a small aquarium. Fifty-three gallons of the stuff per person. That's half a liter of Diet Coke on an average day. Compare that to our other favorite liquid-caffeine companion. For every cup of coffee we consumed in 2003, we drank two cups of soft drink. For $1 we spent on joe, we spent $4 on soda.

Now look where we are: Soda is in a free fall, with domestic revenue down 40%. Coffee culture is ascendant, up 50% in ten years. In another decade, the United States could easily spend more on coffee than soda -- something utterly unthinkable at the turn of the century (industry data via IBISWorld)

Tea production and coffee shop revenue not included; soda data includes
major industry players, including revenue from Coca Cola and Pepsico, who together
make up 78 percent of the market; excludes still beverage):

Four factors behind this remarkable caffeinated convergence:

(1) The health thing. This hardly requires summary. Soda ain't cigarettes, but sugary soft drinks have faced a similar cultural and political backlash in the last decade. As obsessively healthy attitudes have osmosed from yoga yuppies to the general population, local governments have turned on soda, pressing school bans and cup-volume limits. Fading consumer sentiment has had twin impacts: pushing soda drinkers to switch to cheaper brands and encouraging soda companies to shift toward diet drinks, smaller bottles, and alternative drinks, according to IBISWorld.

(2) The water and energy-drink craze. Americans drink about 180 gallons of liquid every year. That number is practically carved in stone. It's zero-sum. When a soda drinker decides she wants to drink iced tea with lunch from now on, she's won't order a Diet Coke and an iced tea. She'll just switch. (The economic term for swapping one product for another is called, simply, substitution.)

(3) Ascendant coffee culture. Coffee consumption in the U.S. is basically flat, after two decades when Starbucks and other national coffee shops sprouted like a steroidal ragweed along urban and suburban sidewalks. But young consumers haven't yet had their fix, and as this demographic trades up for more expensive coffee when the economy recovers, IBISWorld projects the overall industry to continue buzzing. Just as studies showing the ill effects of sugary drinks have hurt soda, studies showing we can basically drink as much coffee as we want permit young people to go back for refills. Consumption has increased the most for consumers between 18 and 24, IBISWorld finds, and "younger consumers are more likely to drink coffee on a daily basis today than five years ago" and the most likely to drink espresso drinks.

(4) Rising coffee prices. Coffee's growth isn't just a matter of trading up to more expensive lattes, it's also a case of paying more each year for the same cup. "Much of the revenue growth in the past five years was stimulated by a 14.1% annualized increase in the world price of coffee," which were mostly passed on to customers, IBISWorld found.